This invention relates an improved apparatus for receiving signatures from a printing press or the like, and for collating and stacking the signatures in an overlapping array.
A typical method of printing provides for a continuous web of paper to be printed in discrete, identical segments called signatures. After printing on the continuously web, the signatures are cut or separated one from the other, stacked and then delivered to subsequent stages in the process of manufacture of a newspaper, magazine or the like. Various mechanisms have been proposed for receipt of the printed web, cutting of the web into discrete signatures or sheets and stacking of the signatures. European Patent Application No. 0,244,650, published Nov. 11, 1987, discloses a sheet diverting and delivery system assigned to Littleton Industrial Consultants, which is designed, inter alia, to accomplish the objective of forming discrete signatures into a stack of signatures. That application is incorporated herewith by reference and constitutes prior art to the present invention.
The mechanism disclosed in the Littleton Industrial application depicts a web which is received between a series of rollers and which is cut into discrete lengths using a rotary cutter. The discrete lengths of the web are then fed into a diverter where alternate sheets are diverted to an upper and lower series of conveyors. The sheets received by the upper and lower series of conveyors are each conveyed at a reduced speed relative to the press web speed and are overlapped one on top of the other to form a stack of signatures. This is accomplished by means of a series of endless belts which convey and transport the sheets.
The prior art Littleton Industrial construction thus provides a single stage mechanism to slow the speed of the discrete, separate signatures and to stack or overlap them. The mechanism by which the signatures are delayed or slowed utilizes engagement of the trailing edge of the separate signatures. The construction allegedly provides for a maximum sheet flow rate of somewhere in the vicinity of 1600 to 1700 feet per minute. The Littleton Industrial construction thus does not accommodate the operation of modern presses at maximum press output. That is the construction disclosed by the Littleton Industrial application for patent has not been observed by applicant to be useful for final stacking or overlapping of signatures at full press speeds of modern presses which typically have an output of 60,000 or more impressions per hour and operating speeds of 2,000 feet per minute. Thus there is a need for an improved construction or apparatus for receipt of discrete signatures from a modern press operating at full capacity and for combining the signatures in an overlapped stack or array which moves at a speed less than full press speed.